The thermal sensitivity of certain electronic components employed in contemporary integrated motor systems imposes limits upon the maximum temperature of operation, and thereby precludes optimal performance. Electronic power switching devices, resistors, and like components add significantly to the quantity of heat that is generated by the motor itself, and the problem is exacerbated in small integrated motor systems where the space available within the housing is very limited (typically in the range of about four to five cubic inches, for NEMA size 23 motors to about 10 cubic inches for NEMA size 34 motors).
These factors are not adequately addressed in conventional integrated motor systems. All electrical components, including for example heat-generating MOSFETs and heat-sensitive microprocessors (and other integrated circuit devices), are typically contained in a common, closed space defined within the motor drive housing, and the parts and components of the system are not positioned for optimal transfer and dissipation of heat.
The prior art does however recognize the desirability of providing cooling effects in integrated motor systems of the kind to which the present invention is directed. Japan Publication No. 60-166264 (Application No. 59-55238) provides a step motor in which a fan is mounted on the motor shaft in the driver housing, for the purpose of cooling drive circuit components. It will be appreciated that the space and structural requirements for accommodating and adequately supporting a fan necessarily and substantially increase the size and weight of the overall system, thereby making the arrangement of the Japanese publication particularly unsuitable for use in small, integrated motor systems.